Zinc stearate composition



Oct- 8, 19 7 I G. M. DAVIS ETAL 2,809,121

ZINC STEARATE COMPOSITION filed Sept. 7, 1955 2 Sheets-Sheet 1 lNVENTORS GERALD M DAVIS ROBERT W STAFFORD PATENT ATTORNEY Oct. 8, 1957 e. M. DAVIS ET AL zmc STEARATE COMPOSITION 2 Sheets-Sheet 2 Filed Sept. 7, 1955 V SA RD mm N Wm Wm E G ROBERT w STAFFORD PATENT ATTORNEY United States atent ZINC STEARATE COMPOSITION Gerald M. Davis, Clark, N. J., and Robert W. Stafiord,

Darien, Conn, assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application September 7, 1955, Serial No. 532,886

8 Claims. (Cl. 106-243) This invention relates to zinc stearate compositions and more particularly to compositions wherein the major ingredient consists of zinc salts of higher fatty acids of about 14-22 carbon atoms, which acids are known and sold commercially as stearic acid. More specifically, the present invention relates to these zinc salts which are characterized by a relatively large crystal size. The invention includes the compositions themselves, which will subsequently be described in greater detail, and methods for their preparation.

Most of the zinc stearate of commerce is made from relatively cheap grades of stearic acid which is actually a mixture of stearic acid, palmitic acid and unsaturated acids, usually oleic acid, or a hydrogenated tallow or fish oil fatty acid containing several higher fatty acids of from 14 to 22 carbon atoms and include both saturated and unsaturated acids. The principal commercial source of these hydrogenated fatty acids is tallow and the acids are therefore sometimes referred to as tallow fatty acids. They are usually prepared from the tallow or other similar triglycerides by countercurrent hydrolysis at elevated temperatures, usually accompanied by distillation, and the resulting fatty acid mixture is refined by freezing and pressing or by solvent extraction. Single and double press tallow fatty acids, which are typical of the materials used in practicing the present invention, have the following composition:

Acid

Myristic percent by weight 7 1-4 Palmitic d0 25-52 Stearic do 22-72 Arachidic do 0-24 Behenic do 0-14 Oleic do 5-11 Linoleic do 0-2 Iodine value 3-16 Zinc stearate prepared from acid mixtures of the above type is frequently used in lacquers and other surface coating compositions as a flatting agent and sanding sealing agent. When used for these purposes, a composition having a relatively large average crystal size is desired, with a minimum of fines of less than 1 micron in diameter. The fiatting emciency, the sanding scaling properties and the viscosity characteristics of the lacquer would be improved if zinc stearates having an average crystal size on the order of from about 1 to about 7 microns or larger were available with not more than about 5% by weight having a size of less than about 1 micron. This has been established as desirable inasmuch as zinc stearate crystals in the range of from about 0.1 to about 1 micron or slightly larger have been found to give poor flatting and to form a gel in the lacquer or other material either during grinding or upon subsequent storage.

It is therefore a principal object of the present invention' to provide zinc stearates having a relatively large 2,809,121 Patented Oct. 8, 1957 average crystal size with improved efiiciency as a fiatting and sanding sealing agent in lacquers and other surface coating compositions and exhibiting decreased gelling tendencies during working or on storage.

it has been found that the average crystal size of zinc salts of commercial stearic acids of the type described above is materially increased when relatively minor amounts of phthalic acid or maleic acid are reactively present during the zinc salt formation. Although the invention is not dependent on any particular theory of action, it is believed that the presence of the phthalic acid radical or maleic acid radical in the commercial stearic acid modifies the crystal habit of the resulting zinc salts in such a manner that larger crystals are formed. The invention in its broadest aspects therefore consists in the provision of zinc stearate compositions composed of zinc salts of mixtures of a relatively larger proportion of commercial stearic acid and a minor proportion of phthalic acid, maleic acid or mixtures thereof, such compositions being characterized by good grinding properties and flatting efiiciency in lacquers, varnishes and other surface coating compositions and possessing decreased gelling tendencies.

The proportion by weight of phthalic acid, maleic acid or phthalic-maleic acid mixture to be employed will depend somewhat on the average crystal size desired in the final zinc stearate composition. Improvement in crystal size is noticeable when as little as 3% of the phthalic or maleic acid is present, based on the weight of the stearic acid-dicarboxylic acid mixture, but for most purposes at least about 5% by weight of these acids should be used. Larger quantities up to about 20-30% on the weight of the mixed acids Will increase the average crystal size still further and may be used. For most practical purposes about 5-20% by weight of the phthalic or maleic acid or mixture thereof represents the preferred range, the balance of the acid mixture consisting of fatty acids of within the range of from 14 to 22 carbon atoms such as the single or double press fatty acid referred to above or mixtures of fatty acids equivalent thereto.

The novel zinc stearate compositions of the present in vention may be prepared by mixing the requisite quantity of phthalic acid, maleic acid or a mixture thereof (or the anhydrides of such acids) with tallow fatty acids or other comparable commercial stearic acid, as described above, and converting the resulting mixture into the zinc soap thereof. This is usually done by first forming alkali metal salts of the acids and reacting them with a water-soluble zinc salt such as zinc sulfate or zinc chloride. Preferably this reaction is carried out by using hot aqueous solutions of the reagents; for example, a solution of the sodium or potassium salts of the mixed acids in Water may be run into a reaction vessel simultaneously with a hot solution of zinc sulfate, preferably with continuous agitation. Alternatively, the zinc salt solutions may be added to an agitated solution of the sodium or potassium salts of the fatty acids and phthalic or maleic acid at temperatures in the range of about 60-85 C. In any event, the precipitated zinc stearate composition is recovered by filtration, is washed free of inorganic salts, and is dried at relatively low temperatures on the order of from about 70 press stearic acid and 10% phthalic acid; Figure 2 represents an electron micrograph (9500 X) of a zinc salt of a 100% single press stearic acid; and Figures 3 and 4 represent electron micrographs (9500 X) of a zinc salt of a mixture of 90% single press stearic acid and 10% maleic acid.

The invention will be further described and illustrated by the following specific examples, taken with the attached drawings which are electron micrographs showing the crystal sizes of the products obtained. It will be understood, however, that although these examples may describe certain specific features of the invention, they are given primarily for illustrative purposes, and the inven tion in its broader aspects is not limited thereto.

Example 1 A mixture of 450 parts by weight of single press tallow fatty acid having the following composition:

and 50 parts by weight of phthalic acid were charged into a reaction vessel equipped with an agitator and thermometer. To this mixture of acid was added a solution of 100 parts of 98% sodium hydroxide in 16,000 parts of water with constant agitation and the solution was maintained at'about 75 C. until the sodium salt formation was complete. The resulting solution was held at about 75' C. while a previously prepared solution of 240 parts by weight of zinc sulfate in 1500 parts of water was added thereto. The resulting precipitate was filtered, washed and dried at 75 C. for 12 to 15 hours.

i The character of the product obtained is shown by Fig. l of the drawings, which is an electron micrograph magnified 9500 times of typical crystals of this material. The crystals range in size from about 1 to about 10 microns with not more than about 1% by weight less than 1 micron. A

Fig. 2 of the drawings is an electron micrograph, at the same magnification as Fig. 1, of a commercial zinc stearate produced from the same fatty acid mixture by the same manufacturingprocess, but without the addition of phthalic or maleic acid. It will be noted that the average size of the crystals is smaller and that a larger proportion of the crystals are on the order of 1 micron in size or smaller.

Example 2 The procedure of Example 1 was followed except that 50 parts by weight of maleic acid were substituted for the 50 parts of phthalic acid. The character of the product obtained is shown by Figs. 3 and 4 of the drawings, which are electron micrographs magnified 9500.

Example 3 A mixture of 475 parts by weight of single press tallow fatty acid having the following composition:

Myristic acid percent 2 Palmitic acid do 48 Stearic a id o 39 Oleic acid do 10 Linoleie aciddo 1 Iodine value l5 and 25 parts by weight of phthalic acid were charged into a reaction vessel equipped with an agitator and thermometer. To this mixture of acids was added a solution of 100 parts of 98% sodium hydroxide in 16,000 parts of water with constant agitation and the solution was maintained at about 75 C. until the sodium salt formation was complete. The resulting solution was held at about 75 C. while a previously prepared solution of 240 parts by weight of zinc sulfate in 1500 parts of water was added thereto. The resulting precipitate was filtered,

washed and dried at 80 C. for 12 to 15 hours. The

product analyzed as follows:

Total ash percent 18.50

Washed ash do 16.98

Moisture do.. 0.30 7 Acid value 1.96

Apparent density 4.3

The resulting zinc salt of this mixture of acid ranged in size from about 1 to about 8 microns and possessed excellent fiatting characteristics.

Example 4 A mixture of 375 parts by weight of single press tallow fatty acid having the following composition:

and 125 parts by weight of maleic acid were charged into a reaction vessel equipped with an agitator and thermometer. To this mixture of acids was added a solution of 100 parts of 98% sodium hydroxide in 16,000 parts of water with constant agitation and the solution was maintained at about C. until thesodium salt formation was complete. The resulting solution was held at about 75 C. while a previously prepared solution of 240 parts by weight of zinc sulfate in 1500 parts of water was added thereto. The resulting precipitate was filtered, washed and dried at C. for 12 to 15 hours. The product analyzed as follows:

The resulting zinc salt crystals ranged from about 0.8 to about 5 microns and demonstrated excellent flatting characteristics.

Example 5 A mixture of 400 parts by weight of single press tallow fatty acid having the following composition:

and 50 parts of phthalic acid and 50 parts by weight of maleic acid were charged into a reaction vessel equipped with an agitator and thermometer. To this mixture of acids was added a solution of 100 parts of 98% sodium hydroxide in 16,000 parts of water with constant agitation and the solution was maintained at about 75 C. until the sodium salt formation was complete. The resulting solution was held at about 75 C. while a previously prepared solution of 240 parts:- by weight of zinc sulfate in 1500 parts of water was added thereto. The resulting precipitate was filtered, washed and dried at C. for 12 to 15 hours. The resulting zinc salt crystals demonstrated excellent flatting characteristics.

Example 6 A mixture of 450 parts by weight of double press tallow fatty acid having the following composition:

Myristic acid percent 2 and 50 parts by weight of phthalic acid were charged into a reaction vessel equipped with an agitator and thermometer. To this mixture of acids wasadded a solution of 100 parts of 98% sodium hydroxide in 16,000 parts of water with constant agitation and the solution was maintained at about 75 C. until the sodium salt formation was complete. The resulting solution was held at about 75 C. while a previously prepared solution of 240 parts by weight of zinc sulfate in 1500 parts of water was added thereto. The resulting precipitate was filtered, washed and dried at 105 C. for 2 to 4 hours. The product analysis was obtained.

Total ash percent 17.58 Washed ash do 16.80 Moisture do 0.35 Acid value- 0.84 Apparent density 3.7

The resulting zinc salt exhibited excellent flatting properties.

Example 7 A mixture of 450 parts by weight of single press tallow fatty acid having the following composition:

Myristic aci percent 2 and 50 parts by weight of phthalic acid were charged into a reaction vessel equipped with an agitator and thermometer. To this mixture of acids was added a solution of 100 parts of 98% sodium hydroxide in 16,000 parts of water with constant agitation and the solution was maintained at about 75 C. until the sodium salt formation was complete. The resulting solution was held at about 75 C. and was added simultaneously with a previously prepared solution of 240 parts by weight of zinc sulfate in 1200 parts of water to 300 parts of water with good agitation. The resulting precipitate was filtered, washed and dried at 105 C. for 2 to 3 hours. The resulting zinc salt exhibited excellent flatting characteristics.

Example 8 A mixture of 450 parts by weight of a hydrogenated fish oil fatty acid having the following composition: Myristic acid percent 4 and 50 parts by weight of phthalic acid were charged into a reaction vessel equipped with an agitator and thermometer. To this mixture of acids was added a solution of 100 parts of 98% sodium hydroxide in 16,000 parts of water with constant agitation and the solution was maintained at about 75 C. until the sodium salt formation was complete. The resulting solution was held at about 75 C. while a previously prepared solution of 240 parts by weight of zinc sulfate in 1500 parts of water was added thereto. The resulting precipitate was filtered, Washed and dried at 105 C. for 2 to 3 hours.

6 Example 9 A mixture of 450 parts by weight of a hydrogenated tallow fatty acid having the following composition: Myristic a i percent..- 1.5 Palmitic acid o..-" 28.0 Stearic acid do 64.5 Oleic. acid do 6 Iodine valu 6 and 50 parts by weight of phthalic acid were charged into a reaction vessel equipped with an agitator and thermometer. To this mixture of acids was added a solution of parts of 98% sodium hydroxide in 16,000 parts of water with constant agitation and the solution was maintained at about 75 C. until the sodium salt formation was complete. The resulting solution was held at about 75 C. while a previously prepared solution of 240 parts by weight of zinc sulfate in 1500 parts of water was added thereto. The resulting precipitate was filtered, washed and dried at C. for 1 to 2 hours. The product analyzed as follows:

Total ash percent 15.80 Washed ash d0 15.30 Moisture do 0.35 Acid value 0.56 Apparent density 4.3

Although these examples show the use of phthalic acid and maleic acid, it is, of course, evident that phthalic anhydride and maleic anhydride could equally have been used.

In a similar way, it is to be noted that the use of single press and double press fatty acids is the preferred form of the invention. This, however, is not intended to be limitative of the invention and it is to be observed that in the last two examples, hydrogenated fatty acids were used which possessed similar compositions by weight of the fatty acids as well as iodine values falling within the range of from about 3 to about 16. Consequently, it may be stated that any mixture of fatty acids having the composition of fatty acids hereinbefore defined, as well as iodine values between 3 and 16, will be applicable to the inventive concept here involved.

The product of Examples 1 and 2 were tested in nitrocellulose sanding sealers for wood in comparison with a sample of a presently used commercial zinc stearate shown in Fig. 2 of the drawings. Grinds were prepared containing 20 parts by weight of the zinc stearate under test, 6.6 parts of 0.5 second nitrocellulose, 3.6 parts of ethanol, 22.9 parts of 60:40 toluene-ethyl acetate mixture and reduced to 30.2% solids with a 10-10102010-40 mixture of butyl acetate, ethyl acetate, methylethyl ketone, hexane, butanol and xylene (solvent A). Additional nitrocellulose, resin and solvents were added after grinding to make the following sealer compositions.

Parts by weight Zinc Stearate 20 The test results on these lacquers were as follows:

Zine stearate Example 1 Example 2 Commercial Grind Fluidity Solids at 21 sec. #4 Ford Oup Sanding Ease (10=best) Haze (Note 1) Excellent Exoellen 9 Sealing Efficiency 10 10 10 N01212: 1.1he tests were made on walnut panels filled with blown linseed Oll filler, dlled 1 week, sealed, sanded, topcoated with a standard lacquer and. polished.

The stearates were also tested in flat lacquers made of a grind of 19.5 parts (6% on resin solids) of zinc stearate, 100 parts of 0.5 second nitrocellulose, 225 parts of alkyd resin (Rezyl 50-5) and thinned with solvent'A to the viscosity indicated below. The "test results were:

These results show that the zinc stearates of the invention develop lower viscosities on grinding and possess much better flatting efficiency (lower gloss) than are obtained with commercial zinc stearates of smaller crystal size.

From the foregoing it will be seen that the present invention provides a ready means of increasing and controlling the crystal size of zinc stearates obtained from commercial fatty acid mixtures of the type exemplified by single and double press tallow fattyacids. Zinc salts of these fatty acid mixtures are usually obtained in the form of fine crystals having an average particle size on the order of only about'1I5' microns with an undesirably larger proportion less than 1 micron. However, by the incorporation of small amounts of maleic or phthalic acids into these commercial fatty acid mixtures, preferably in quantities of from 5 to about 20% by weight, the average crystal size of the resulting zinc stearate composition can be increased to a value within the range of 5-10 microns or larger, with only a minor proportion having a size smaller than 1 micron in diameter and with a substantial improvement in the eflicicncyof the material as a flatting agent for lacquers and varnishes.

We claim:

1. A zinc stearate composition composed of zinc salts 8 of a mixture of about -97% by weight of fatty acids of 14-22 carbon atoms and 3-30% by weight of a member of the group consisting of ,pht'halic and maleic acids.

2.. A composition as defined in claim -1 wherein the fatty acids contain from 14 to 4-8 carbon atoms.

3. YA zinc stearate composition composed of zinc salts of amixture of about -95% by weight of fatty acids of 14-22 carbon atoms and 5-20% by weight of a member of the group consisting of .phthalic and maleic acid.

4. A composition as defined in claim 3 wherein the fatty acids contain from 14-18 carbon atoms.

5. A composition as defined in claim 3 wherein the fatty acids are hydrogenated tallow fatty acids.

6. A composition as defined i-n claim 3 wherein the fatty acids are hydrogenated fish oil fatty acids.

7. A method of producing a zinc stearate composition characterized by large crystals and good grinding properties and flatting eificiency in surface coatings which comprises mixing an aqueous solution of a water-soluble zinc salt with an aqueous solution of alkali metal salts of a mixture of 70-97% by weight of fatty acids of 14-22 carbon atoms and 3-30%' by weight of a member of the group consisting of phthalic and maleic acids, and recovering and drying the resulting precipitate.

8. A method of producing a zinc stearate composition characterized by large crystals and good grinding properties and fiatting efiiciency in surface coatings which comprises preparing an aqueous solution of alkali metal salts of a mixture of about 5-20% by weight of a member of the group consisting of phthalic and maleic acid and 80-95% by weight of fatty acids of 14-22 carbon atoms, reacting said solution with an aqueous solution of a water-soluble zinc salt, and recovering and drying the resulting precipitate.

No references cited. 

1. A ZINC STEARATE COMPOSITION COMPOSED OF ZINC SALTS OF A MIXTURE OF ABOUT 70-97% BY WEIGHT OF FATTY ACIDS OF 14-22 CARBON ATOMS AND 3-30% BY WEIGHT OF A MEMBER OF THE GROUP CONSISTING OF PHTHALIC AND MALEIC ACIDS. 